bearing description about basic, types, failure causes

BEARINGS

A bearing is a device to permit constrained relative motion between two parts, typically rotation or linear movement.

Bearings may be classified broadly according to the motions they allow and according to their principle of operation

BEARINGS

FUNCTION OF A BEARING• The main function of a rotating shaft is to transmit power

from one end of the line to the other.

• It needs a good supportsupport to ensure stabilitystability and frictionless rotation. The supportsupport for the shaft is known as “bearing”.

• The shaft has a “running fit” in a bearing. All bearing are provided some lubrication arrangement to reduced friction between shaft and bearing.

• Hold &Guide to shaft• Smooth & Free motion to Save power

Types of Bearings

CLASSIFICATION OF BEARINGSBEARING

ANTIFRICTION BEARING FRICTION BEARING

Friction Bearing

• Hydrostatic bearing• Hydrodynamic or Journal Bearing 1.Solid or Bush bearing 2. Split bearing• Bearing Material:-CI Brass, Bronze Gun

metal Babbitt metal or White metal

Bearings -continuedHydrostatic Bearing

Hydrodynamic Bearing

ANTI FRICTION BEARING

• BALL BEARING

• ROLLER BEARING

• TH RUST BEARING

Rolling Element Bearing Parts

The parts and nomenclaturefor a Ball Bearing

Outer Race

Inner Race

Ball

Cage or Separator

Bore

Roller Bearings

Needle Roller Tapered Roller Spherical Roller

BALL BEARING• Deep Groove Ball Bearings • Self Aligning Ball Bearings • Angular Contact Ball Bearings

ROLLER BEARING•Cylindrical Roller Bearings •Needle Roller Bearings •Spherical Roller Bearings •Taper Roller Bearings

DEEPGROOVE BALL BEARING 

Deep groove ball bearings are capable of operating at high speeds and are widely used radial bearings. These non-separable bearings are available in a wide variety of seal, shield and snap-ring arrangements. It requires little attention or maintenance in service.

Accommodates Radial and Axial Loads

High SpeedsLow Friction

Locating BearingSeals/Shields

Single Row Deep GrooveBall Bearing

Advantages Of Deep Groove Ball Bearings

• Can sustain radial, axial, or composite loads. • Can provide both high-running accuracy and

high-speed operation. • Can take the place of high speed angular

contact ball bearings. • Simple design. • Maintenance free. • Longer service life.

Application Of Deep Groove Ball Bearings

• axial loads from two directions have to be transmitted, and existing space does not allow installation of matched spindle bearings.

• best possible guidance of rotating parts is required and speed is less important.

Deep Groove Ball Bearings

• Industrial– Electric Motors/Power Tools– Gearboxes, Transmissions– Pumps/Compressors– Office Automation

• Automotive– Alternators/Starters– Cooling Fans– ABS Motors

Applications

Internal ClearanceRadial Internal Clearance

Axial Internal Clearance (end play)

Bearing Basics

Thrust

Radial force F ShaftBearing

Housing

Axial

Radial

Bearing Loads

Radial loads originate from the

• Weight of the shaft• Weight of the pulley• Tension of the belt• Weight of the propeller• Propeller rotation

Angular Contact Ball Bearings

Angular contact ball bearings are non-separable type bearings and typically used for carrying combined (axial and radial) loads. They can carry pure axial load and operate in higher speed. That's why many people refer to them incorrectly as thrust bearings

Thrust load

Radial load

Radial load

Thrust load

Angular Contact Ball Bearings• Accommodates Radial Loads, also

Axial Loads in One Direction • Greater Axial Load Capacity than

Single Row Deep Groove Bearings• High Rigidity with Preload• Frequently Sold as Matched Sets• High Speed• Low Friction• Locating In One Direction

Types Of Angular contact ball bearings

Single Row Bearings Double Row Bearings

Four Point Contact Ball Bearings

There are three basic types of angular contact ball bearings

Single Row Angular Contact Ball Bearings:

Double Row Angular Contact Ball Bearings

Four Point Contact Ball Bearings

Angular Contact Ball Bearings

• Pumps & Compressors• Metal Rolling Mills• Electric Motors &

Generators• Machine Tool Spindles• Automotive Hub Bearings

Applications

Double Row Angular Contact• Equivalent to Two Bearings mounted

Back to Back• Accommodates Radial Loads and

Axial Loads in Both Directions• One Piece Outer Ring / Inner Ring• Reduces Width RequiredApplications

– Centrifugal Pumps– Electric Motors– Blowers & Fans– Transmissions/Gearboxes

Self Aligning Ball Bearings Self aligning ball bearings are suitable for applications where misalignment can arise from errors in mounting or shaft deflection. The steel balls, cage, and inner ring can rotate freely at a certain angle, as it is stated that the bearings have self-aligning features.

Self Aligning Ball Bearings Specifications & Standards

• Standard cage types - All bearing series are equipped with a pressed cage, except 2322S, which is equipped with a machined cage.

• Misalignment - They are designed to adjust to the angular misalignment from one bearing to the other within the permissible limits.

• Cages - There are standard cages but some may have pressed steel cage, glass fiber reinforced, or machined brass cages

Advantages Of Self Aligning Ball Bearings

• Have the lowest friction of all rolling bearings.

• Run cooler even at high speeds. • Easy mounting and dismounting. • The permissible operating speed is not

dependent on the common criteria like heat generation or cage stability and strength.

Types Of Self Aligning Ball Bearings

• Basic open design • Sealed Bearings • Bearings with Extended Inner Ring

The two basic designs of double row self-aligning ball bearings are standard and "E" shaped. The "E" shaped have a larger load carrying capacity and can be used in a wider range of applications

They are available in three designs:

Application Of Self Aligning Ball Bearings

• Self-aligning ball bearings are used for commercial ground shafting applications.

• Since axial load capacity is limited, self-aligning ball bearings are not suitable for applications with heavy axial loads.

• Furthermore, if an adapter is used on the tapered bore of the inner diameter, installation and disassembly are much simpler and for this reason adapters are often used on equipment with drive shafts.

Ball Bearing Characteristics Deep

Groove Angular Contact

D-R Ang. Contact

Duplex Ang. Cont.

Radial Load F G G G

Axial Load F G G G

Combined Load F G G G

High Speed E E F G High Accuracy E E - E

Low noise & Torque E G F G

Angular Misalignment G F P P

E: Excellent G: Good F: Fair P: Poor X: Impossible

Minimum Load – For satisfactory operation, the bearings must be subjected to the minimum load that is calculated by:

Buying TipsSelecting Deep Groove Ball BearingsBefore selecting a deep groove ball bearing you should take note of the followings: Material - Chrome steel, High temperature steel, ball material Maintenance requirements bearing applications Service life Bearing clearance Sealing efficiency Contamination exclusion and grease retention Low-friction seals for energy saving

Types Of Cylindrical Roller Bearings

• Single or Double Row Bearings • Full Complement Cylindrical Roller

Bearings • Crossed Cylindrical Roller Bearing

Cylindrical roller bearings, single row, NU, N, NJ, NUP designs

Cylindrical Roller Bearing Types

NU NJ NUP N

Cylindrical Roller Bearings Cylindrical roller bearings use rollers for rolling elements, and therefore has a high load capacity. The rollers are guided by ribs on either the inner or outer ring, therefore these bearings are also suitable for high speed applications. The inner and outer rings can be separated to facilitate assembly, and both can be fit with shaft or housing tightly.

Cylindrical Roller Bearings• Very High Radial Load Capacity• Good Speed Capability• Separable Inner or Outer Ring• Limited Misalignment Capability• Rings Can Move Axially During

Operation (within limits)Applications

– Large Electric Motors– Gearboxes/Transmissions,

Presses– Machine Tool Spindles– Steel Mills (Rolling Mills)

Physical Characteristics

Although the rolling elements in cylindrical roller bearings are called "cylindrical," they are not true cylinders. True cylinders would produce stress concentrations at the ends of the roller-race contact, resulting in high wear and high sensitivity to misalignment. Instead, rollers are usually crowned or end relieved.

Application Of Cylindrical Roller Bearings Cylindrical roller bearings are used in power generation, oilfield, mining and aggregate processing, gear drives, rolling mills, machine tools, transmissions, vibration machines and as wheelset bearings for rail vehicles.

Needle Roller Bearings Needle roller bearings use needle rollers as rolling elements. The needle rollers are a maximum of 5 mm in diameter and are 3 to 10 times as long as they are in diameter. Because the bearings use needle rollers as rolling elements, the cross-section is thin, but they have a high load capacity for their size. Because of the large number of rolling elements, the bearings have high rigidity and are ideally suited to wobbling or pivoting motion.

Needle roller bearing without flanges, double row, without an inner ring

Needle roller bearing with flanges, single row, with an inner ring

Needle roller bearing with flanges, single row, without an inner ring

Physical Characteristics

• referred to as needle rollers. • Needle Rollers are used for needle roller

bearings and are rigid and highly accurate. • In spite of their low cross section the

bearings have a high load carrying capacity. • Available with or without an inner ring. • The needle rollers are a maximum of 5 mm

in diameter and are 3 to 10 times as long as they are in diameter.

Advantages of Needle Roller Bearings

• Due to the smaller cross-section, greater rigidity, higher load-carrying capacity and lower inertia of the needle roller bearings help size and weight reductions in the machinery.

• Though they are less wide, their load carrying capacity is high and is most suitable for applications where the load is high and the radial space is less.

• Needle roller bearings, which are designed to withstand oscillation can operate under severe conditions and interchange with sliding bearings.

Typical Applications

• Transmissions, transfer cases, engines and valve trains

• Steering and braking systems • Axle support

• Power tools • Copiers, fax machines, paper-moving

equipment • Appliances

Spherical Roller Bearings

Spherical Roller Bearings• High Load Carrying Capacity

– Heavy Radial Loads/Impact Loads

– Moderate Axial Loads– Different Series Carry Different

Ratio of Radial and Axial Loads• Fair Speed Capability• Can Take Misalignment

– Up to 11/2 o

– No Loss in Capacity• Typically Two-Rows

Spherical Roller Bearings

• Steel Mills• Paper Mills• Continuous Casting

Machinery• Aggregate Equipment• Large Gearboxes• Large Air Handling

Equipment

Applications

Physical Characteristics • Spherical roller bearings consist of an outer ring

having a continuous spherical raceway • Within which operates two rows of barrel-shaped

rollers which are in turn guided by an inner ring with two raceways separated by a center rib.

• This bearing has self-aligning properties, and therefore is suited for use where misalignment between the inner and outer rings occurs from housing installation error or shaft flexure.

• Spherical roller bearings have a large capacity for radial loads, axial loads in either direction, and complex loads. .

Tapered Roller Bearings

• Designed for Heavy Axial/Radial Loads In One Direction

• Outer Ring is Separable• Outer Ring is Commonly Called the

Cup• Inner Ring (w/ rollers & retainer) is

Commonly Called the Cone• Fixed Contact Angle

• Limited Misalignment Capability• Locating in One Direction

Radial load

Radial load

Thrust load

Thrust load

Taper Roller Bearings The taper roller bearings can carry combinations of large radial and thrust loads or thrust load only. Because of the difference between the inner and outer raceway contact angles, there is a force component, which drives the tapered rollers against the guide flange. The relatively large sliding friction generated at this flange makes this bearing typically unsuitable for high-speed applications without special consideration to coolant / lubricant. Typical applications include construction machinery, gear construction, vehicle manufacture and rolling mills.

Tapered Roller Bearings• Available in Inch (ABMA)

or Metric (ISO) Series• Single Row• Double Row

– Duplexed– Double Cup or Cone

Advantages Of Taper roller bearings

• Dimensional Stability • Long Life Even In Contaminated Lubricant • Durable Steel Cage • Dimensionally Interchangeable With Other

Bearing Manufacturers

Types Of Taper Roller Bearings

• Single-row tapered roller bearings • Double-row tapered roller bearings • Four row tapered roller bearings

Minimum load - For satisfactory operation, the bearings must be subjected to the minimum load that is calculated by

Frm = 0,02 C

whereFrm , =, minimum radial load, kNC, =, basic dynamic load rating

Physical Characteristics • Taper roller bearings have tapered inner and

outer ring raceways between which tapered rollers are arranged.

• The projection lines of all the tapered surfaces meet at a common point on the bearing axis. Their design makes taper roller bearings particularly suitable for the accommodation of combined (radial and axial) loads.

• The axial load carrying capacity of the bearings is largely determined by the contact angle. The larger the angle, the higher the axial load carrying capacity.

Tapered Roller Bearings

• Automotive Uses– Differential– Transmissions– Heavy Duty Wheel Bearings

• Aircraft Wheel Bearings • Heavy Duty Industrial Gearboxes• Steel Mill Guide Boxes/Work

Rolls (Rollneck)• Plastic/Metal Forming Equipment

Applications

Applications Of Taper Roller Bearings

• In many applications taper roller bearings are used in back-back pairs so that axial forces can be supported equally in either direction.

• Pairs of taper roller bearings are used in car and vehicle wheel bearings where they must cope simultaneously with large vertical (radial) and horizontal (axial) forces.

• Agriculture, Construction and Mining Equipment • Various Axle Systems • Conveyance Vehicles • Gear Box, Engine Motors, Reducers

Thrust Bearings

• Thrust Ball Bearings • Angular Contact Thrust Ball Bearings • Cylindrical Roller Thrust Bearings • Needle Roller Thrust Bearings • Spherical Roller Thrust Bearings • Taper Roller Thrust Bearings

Thrust Ball BearingsThrust Ball Bearings carry pure thrust (axial) loads. When a load is properly applied to this bearing, the internal contact points are aligned on a plane parallel to the shaft. Radial loads dislodge the balls from their track. Thrust ball bearings can be single direction and double direction designs

Needle Roller Thrust BearingsNeedle roller thrust bearings are for heavy axial loads. They require a minimum axial space and are arranged rather stiffly. They can accommodate axial loads acting in one direction i.e. they are single direction bearings. It can take as less space as a thrust washer can. The roller, cage and the raceways can all be separated and be combined with washers of various designs.

Cylindrical Roller Thrust BearingsCylindrical roller thrust bearings are suitable for heavy axial load accommodation. They are relatively insensitive to shock loads. They are very stiff and require little axial space. They are most commonly available as single direction bearings and can accommodate axial loads acting in single direction. Cylindrical thrust bearings may be produced in single row and double row designs. Double row patterns are mainly used where thrust ball bearings have insufficient load carrying capacity

Needle Roller Thrust BearingsNeedle roller thrust bearings are for heavy axial loads. They require a minimum axial space and are arranged rather stiffly. They can accommodate axial loads acting in one direction i.e. they are single direction bearings. It can take as less space as a thrust washer can. The roller, cage and the raceways can all be separated and be combined with washers of various designs.

Taper Roller Thrust BearingsTaper roller thrust bearings enable axially very compact bearing arrangements and capacity to carry very heavy axial loads, are insensitive to shock loads and are stiff.

Roller Bearing Characteristics

Cylindrical

Spherical

Taper

Toroidal Radial Load G E G E

Axial Load X/P F G X

Combined Load X/F G G X

High Speed E F G G High Accuracy G F G F Low Noise & Torque G F F -

Angular Misalignment F E F E

E: Excellent G: Good F: Fair P: Poor X: Impossible

Bearing Characteristics ComparisonBearing Types

Radial load capacity

1 2 3 4

Thrust (Axial) load capacity

1 2 3 4

Relative permissible speed

1 4 7 10 13

Deep Groove Ball Bearings

Angular Contact Ball Bearings

Cylindrical Roller Bearings

Tapered Roller Bearings

Spherical Roller Bearings

Oil Bath lubrication With special measures to increase speed limit

Bearing Characteristics Comparison

50 x 90 mm Basic Dynamic load rating (Cr)

Basic Static load rating (C0r)

Limiting Speed (Open with oil

lub.) RPM Single row deep groove ball brg.

6210 35,000 N 23,200 N 8,500 RPM

Angular contact ball bearing

7210B

Single – 37,500 N

Pair – 60,500 N

Single – 28,600 N

Pair – 57,000 N

Single – 8,000

Pair – 6,300 Cylindrical roller

bearing NU210E

69,000 N 76,500 N 7,500 RPM

Taper roller brg. 32210 87,500 N 109,000 N 5,300 RPM

Spherical roller bearing 22210

99,000 N 119,000 N 6,300 RPM

Selection of bearing type • Available space• Loads• Misalignment• Precision• Speed• quiet running• Stiffness• axial displacement• mounting and dismounting• integral seals.

The primary contributors to abnormal bearing signaturers

• Imbalance• Misalingment• Rotar instability• Excessive or abnormal loads• Mechanical looseness

Bearing LubricationOil vs. Grease

Advantages1. Better Heat Dissipation2. Higher Speed Capability3. Can be Circulated4. Can be FilteredDisadvantages1. Possibility of Leakage2. Does not Seal3. Can be Displaced by Water4. May Require More

Complicated System

Advantages1. Easy to apply2. Helps to seal3. Wide range of

applications4. Better control of leakage Disadvantages1. Poor heat dissipation2. Collects and retains

contaminants3. Structural change

possibility (i.e. - work hardening)

4. Possible compatibility problems if greases are mixed

OIL

GR

EASE

Bearing LubricationGrease Selection

• Viscosity of base Oil• Consistency• Speed limit• Bleed rate• Noise characteristics• Moisture resistance• Thickener